Boil the pasta with salt water following the instructions on the package, drain. Toss the pasta with olive oil, yogurt, tomato and red pepper pastes.

Meanwhile, saute the onion with olive oil, salt and pepper for 3-4 minutes at medium heat in a large skillet. Stir the garlic until fragrant for about 30 seconds. Then, add the spinach and red pepper. Cook for 2-3 more minutes, turn the heat off.

Add the pasta and stir. Sprinkle some walnuts and feta cheese over the top. Serve immediately.